EP2479305A1 - Procédé de fabrication d'une pièce automobile de structure à partir d'un alliage Al-Zn laminé - Google Patents

Procédé de fabrication d'une pièce automobile de structure à partir d'un alliage Al-Zn laminé Download PDF

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Publication number
EP2479305A1
EP2479305A1 EP11151732A EP11151732A EP2479305A1 EP 2479305 A1 EP2479305 A1 EP 2479305A1 EP 11151732 A EP11151732 A EP 11151732A EP 11151732 A EP11151732 A EP 11151732A EP 2479305 A1 EP2479305 A1 EP 2479305A1
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EP
European Patent Office
Prior art keywords
temperature
formed part
sub
aluminium alloy
aluminium
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Application number
EP11151732A
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German (de)
English (en)
Inventor
Sunil Khosla
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Aleris Aluminum Duffell BVBA
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Aleris Aluminum Duffell BVBA
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Priority to EP11151732A priority Critical patent/EP2479305A1/fr
Publication of EP2479305A1 publication Critical patent/EP2479305A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/10—Alloys based on aluminium with zinc as the next major constituent

Definitions

  • the invention relates to a method of manufacturing a formed aluminium alloy structural part or body-in-white (BIW) part of a motor vehicle, wherein the aluminium alloy is an AA7000-series alloy.
  • aluminium alloy designations and temper designations refer to the Aluminum Association designations in Aluminum Standards and Data and the Registration Records, as published by the Aluminum Association in 2010 .
  • Body-in-white consists of the structural components of the automobile, not including closures (e.g. door panels, hood panels, trunk lid panels).
  • aluminium alloys in particular for formed structural and BIW parts, which are formable and having in particular increased strength after being subjected to a paint bake cycle.
  • the properties normally required for such parts include a high formability for the forming operation (typically by means of stamping, deep drawing, or roll forming), high mechanical strength after paint baking so as to enabling down gauging thus minimising the weight of the part, good behaviour in the various assembly methods used in motor vehicle manufacturing such as spot welding, laser welding, laser brazing, clinching or riveting, and an acceptable cost for mass production.
  • the present invention providing for a method of manufacturing a formed aluminium alloy structural part or a body-in-white (BIW) part of a motor vehicle, the method comprising the steps of:
  • the stamped components may show significant tendency to the formation of cracks not immediately during or upon the forming operation but with some delay of only after a few hours or even firstly after several days in an ambient environment. This phenomena is also referred to as sensitivity to delayed crack formation.
  • the sensitivity to delayed fracture is significantly reduced and it can even be overcome.
  • the time between the forming operation and the cooling of the formed part to sub-zero temperatures is not too critical, but it is preferred to perform the cooling operation within 1 hour after the forming operation, and preferably within 30 minutes after forming, and more preferably if practical from a logistics point of view immediately after the forming operation.
  • the formed part is cooled to a sub-zero temperature T1 (°C), and wherein T1 is in the range of about minus 25°C to minus 200°C. And preferably of about minus 40°C to minus 200°C, thus for example to the temperature of liquid nitrogen (minus 196°C) or to the temperature of dry ice having a temperature of minus 78°C.
  • T1 sub-zero temperature
  • T1 is in the range of about minus 25°C to minus 200°C.
  • preferably of about minus 40°C to minus 200°C thus for example to the temperature of liquid nitrogen (minus 196°C) or to the temperature of dry ice having a temperature of minus 78°C.
  • quenching or cooling to the sub-zero temperature (T1) was performed by cryogenic cooling using liquid nitrogen or dry ice and which are preferred, it should be understood that quenching may also include other types of cooling liquids (dry ice/ethanol, dry ice/acetone, liquid nitrogen/solvent, and the
  • the formed part should be allowed to reach equilibrium at this temperature. Once equilibrium is attained, the formed part will be uniform in temperature.
  • T2 of ambient temperature (about 20°C) or more.
  • ambient temperature about 20°C
  • T2 ambient temperature
  • the upper limit for T2 is about 250°C, and more preferably about 200°C, and even more preferably about 120°C.
  • a preferred lower-limit for T2 is about 40°C.
  • T2 could be about 80°C or about 100°C.
  • This rapid heating from T1 to elevated temperature T2 can be achieved be submerging the formed part into a hot liquid of temperature T2, e.g. boiling water, or by using convection heating or steam (e.g. by transferring of the formed part to a steam chamber having for example nozzles spraying hot water steam onto the formed part, and whereby for a high heat transfer for example high velocity steam is being applied).
  • a hot liquid of temperature T2 e.g. boiling water
  • convection heating or steam e.g. by transferring of the formed part to a steam chamber having for example nozzles spraying hot water steam onto the formed part, and whereby for a high heat transfer for example high velocity steam is being applied.
  • the formed part should be allowed to cool to ambient temperature, for example using regular air cooling, for further processing into a motor vehicle component.
  • the rolled aluminium alloy sheet may be obtained by methods known in the art, and which include continuous casting or DC-casting of a rolling stock, homogenisation and/or preheating of the rolling stock, hot rolling and/or cold rolling to a final gauge typically in the range of about 0.5 to 4 mm. Depending on the alloy composition and the amount of cold work an intermediate anneal may be used before or during the cold rolling operation.
  • the heat treatment such as a SHT and quenching of the sheet product can be carried out as a continuous operation for example using a continuous annealing line, after which the sheet product is being coiled again.
  • the coiled sheet product can then be transported to a press shop for further processing into a formed part.
  • the time between the quenching operation and the forming operation is less than 2 weeks and more preferably less than 4 days.
  • the sheet product following SHT and quenching is artificially aged at a temperature in a range of 50°C to 250°C.
  • a temperature in a range of 50°C to 250°C For example to an underaged T6 temper, e.g. T61, T64 or T65 according to EN515.
  • the sheet product is aged to an over-aged T7x temper, for example a T79 temper.
  • the cold rolled sheet product is subjected to a heat treatment at a temperature placed in a phase field of the aluminium alloy where substantial strengthening is realised following a cooling operation, in particular it can be SHT followed by quenching, near or in the press shop such that the dwell time between cooling and the forming operation is being reduced.
  • a cooling operation in particular it can be SHT followed by quenching, near or in the press shop such that the dwell time between cooling and the forming operation is being reduced.
  • it may still be produced as a coiled product or alternatively firstly uncoiled, then cut in a separate sheet product having smaller dimensions, the cut sheet product being heat treated individually or in a small batch, subsequently cooled and formed, preferably within 4 hours after cooling, into a three-dimensional formed part or component.
  • the heat treated and cooled sheet receives a controlled amount of stretching, typically in a range of 0.5% to 4%, to increase the flatness of the sheet product prior to any subsequent forming operation.
  • the sheet product is compressed, typically in a range of 1% to 5%, for example using a die operation.
  • the sheet product can be formed into a three-dimensional formed BIW part or other structural component configuration of a motor vehicle.
  • the forming operation can be any forming operation used to shape three-dimensional motor vehicle components, and includes in particular operations like stamping, deep drawing, pressing, press forming, and roll forming, either at ambient or at elevated temperature.
  • the sheet product Before shaping, the sheet product may be coated with a lubricant, oil or dry lubricant, suitable for the forming operation, the assembly and the surface treatment of the structural part to be produced.
  • a lubricant oil or dry lubricant
  • the formed part is typically made part of an assembly of other metal components as is regular in the art for manufacturing vehicle components, and subjected to a paint bake operation to cure any paint or lacquer layer applied.
  • the paint bake operation or paint bake cycle typically comprises one or more sequential short heat treatment in the range of 140°C to 200°C for a period of 10 to less than 40 minutes, and typically of less than 30 minutes.
  • a typical paint bake cycle would comprise a first heat treatment of about 180°C@20 minutes, cooling to ambient temperature, then about 160°C@20 minutes and cooling to ambient temperature.
  • such a paint bake cycle may comprise of 2 to even up to 5 sequential steps and includes drying steps, but either way the cumulated time at elevated temperature (100°C to 200°C) of the aluminium alloy product is less than 120 minutes.
  • the method according to this invention can be applied to a wide range of AA7000-series alloys, in particular those that show a tendency to natural ageing.
  • the aluminium alloy is selected from the group of AA7021, AA7136, AA7075, AA7081, AA7085, AA7050, AA7055, and modifications thereof.
  • the AA7000-series alloy comprises, in wt.%, Zn 5.5 to 8, preferably about 6 to 7.5, Mg 1.5 to 2.1 Cu 0 to 0.45 Mn 0 to 0.15, preferably 0 to 0.05, Zr 0.04 to 0.25% Ti 0 to 0.15 Fe 0 to 0.35 Si 0 to 0.25, other elements and unavoidable impurities, each maximum 0.05%, total 0.20%, balance aluminium.
  • the AA7000-series aluminium alloy sheet product has been provided with a metal clad layer applied on at least one side, wherein the metal clad layer material has an inner-surface and an outer-surface and wherein the inner-surface is facing the AA7000-series material.
  • the clad layer or clad layers are usually much thinner than the core sheet, and each clad layer constituting about 1% to 25% of the total composite sheet thickness.
  • a clad layer more typically constitutes around about 1% to 14% of the total composite sheet thickness.
  • the clad layer material can be made from an AA3000, AA4000-, AA5000-, AA6000-, or a different AA7000-series aluminium alloy compared to the core alloy.
  • the clad layer material consists of an AA5000-series alloy having more than 3.8% of Mg. More preferably the clad layer material has more than 4.8% of Mg, and preferably less than 7%, and more preferably less than 5.9%.
  • the characteristics for the pretreatment like phosphating, passivation or alternative processes used at OEM's are improved.
  • Aluminium alloys of the AA5000-series are known to the automotive industry and having an AA5000-series alloy as outersurface results in that there are little or no adjustments required for the surface pretreatment of the composite structure compared to aluminium alloys already in use for automotive applications. Hence there are no problems with existing alloy systems.
  • Another advantage of the composite structure is it can be used for making components having a high impact resistance or good crash performance.
  • the application of an AA5000-series clad layer having a high Mg-content results in a favourable formation of less cracks at the surface as these alloys have a good bendability, while the defined AA7000-series core alloy provides the required high strength.
  • the clad layer material consists of an AA6000-series aluminium alloy to increase the overall corrosion performance of the formed part.
  • Preferred alloys are AA6016 and AA6005-series alloys.
  • the BIW part manufactured according to this invention is an ideal candidate to replace parts made from dual-phase steel such as steel grades dp600, dp800, and boron steels, leading to considerable weight saving opportunities in the motor vehicle.
  • an formed structural motor vehicle part or a BIW part of a motor vehicle the part being made from an AA7000-series aluminium alloy having a gauge in the range of 0.5 to 4 mm, and preferably in the range of 0.7 to 3.5 mm, and wherein the part has been SHT, quenched, formed from sheet into a three-dimensional formed part, and after being formed subject to a heat-treatment by holding it at a sub-zero temperature of less than minus 25°C and the heated to a temperature of more than 40°C and cooled to ambient temperature to reduce the sensitivity to delayed cracking at ambient temperature. Thereafter the heat-treated formed part can be subjected to a paint bake cycle to provide a yield strength of at least 350 MPa, and more typically of at least 400 MPa.
  • the sheet had been resolutionised and quenched (so-called "fresh W-temper") and immediately drawn into a cup using the well-known Erichson drawn-cup-test at ambient temperature and ambient atmosphere. Within 24 hours at ambient temperature and ambient atmosphere the drawn cup showed a serious formation of a series of cracks in the cup as shown in Fig. 1 .
  • drawn cups were within about 2 minutes after drawing quenched in liquid nitrogen and kept at this temperature for about 15 minutes and then reheated to 200°C by transferring the cups to a pre-heated furnace of 200°C and kept at this temperature for about 20-30 minutes and cooled by air cooling to ambient temperature.
  • the cups that being subjected to this heat treatment did not shown any formation of delayed fracture irrespective of the time after completion the heat treatment; thus no crack formation after several months.
  • Five days after this heat treatment several cups had been subjected to a simulated paint-bake cycle and all remained fully intact following this paint-bake cycle.
  • the delayed fracture in drawn cups occurred also in the same sheet material but having been solution heat-treated, quenched and over-aged to a T79 temper prior to the drawing at ambient temperature and ambient atmosphere. Also here the identical heat treatment of quenching to sub-zero temperature and reheating to 200°C in accordance with this invention resulted in the avoidance of crack formation in the drawn cups, and several of these heat treated and drawn cups after 5 days had been successfully subjected to a simulated paint-bake cycle without any crack formation.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
EP11151732A 2011-01-21 2011-01-21 Procédé de fabrication d'une pièce automobile de structure à partir d'un alliage Al-Zn laminé Withdrawn EP2479305A1 (fr)

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EP11151732A EP2479305A1 (fr) 2011-01-21 2011-01-21 Procédé de fabrication d'une pièce automobile de structure à partir d'un alliage Al-Zn laminé

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EP11151732A EP2479305A1 (fr) 2011-01-21 2011-01-21 Procédé de fabrication d'une pièce automobile de structure à partir d'un alliage Al-Zn laminé

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108546858A (zh) * 2018-05-29 2018-09-18 广西南南铝加工有限公司 一种7xxx系铝合金板材及其制备工艺
WO2020016506A1 (fr) 2018-07-17 2020-01-23 Constellium Neuf-Brisach Procede de fabrication de toles minces en alliage d'aluminium 7xxx aptes a la mise en forme et a l'assemblage
CN110846598A (zh) * 2019-11-26 2020-02-28 江西江铃集团新能源汽车有限公司 一种铝合金弧焊处理方法
CN113502421A (zh) * 2021-07-13 2021-10-15 山东省科学院新材料研究所 一种Al-Zn-Mg-Fe系铝合金材料及其制备方法与应用
CN113714511A (zh) * 2021-09-23 2021-11-30 中南大学 电弧增材铝合金构件的热处理与深冷变形复合工艺方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1392722A (en) * 1971-07-05 1975-04-30 Alcan Res & Dev Aluminium alloys
US4159217A (en) * 1976-03-31 1979-06-26 Union Carbide Corporation Cryogenic forming
US6258463B1 (en) * 2000-03-02 2001-07-10 Praxair S.T. Technology, Inc. Anodized cryogenically treated aluminum
FR2846669A1 (fr) * 2002-11-06 2004-05-07 Pechiney Rhenalu PROCEDE DE FABRICATION SIMPLIFIE DE PRODUITS LAMINES EN ALLIAGES A1-Zn-Mg, ET PRODUITS OBTENUS PAR CE PROCEDE
WO2009156283A1 (fr) * 2008-06-24 2009-12-30 Aleris Aluminum Koblenz Gmbh Produit d'alliage al-zn-mg avec une sensibilité à la trempe réduite
JP2010083381A (ja) * 2008-09-30 2010-04-15 Kobe Steel Ltd バンパーシステム及びその製造方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1392722A (en) * 1971-07-05 1975-04-30 Alcan Res & Dev Aluminium alloys
US4159217A (en) * 1976-03-31 1979-06-26 Union Carbide Corporation Cryogenic forming
US6258463B1 (en) * 2000-03-02 2001-07-10 Praxair S.T. Technology, Inc. Anodized cryogenically treated aluminum
FR2846669A1 (fr) * 2002-11-06 2004-05-07 Pechiney Rhenalu PROCEDE DE FABRICATION SIMPLIFIE DE PRODUITS LAMINES EN ALLIAGES A1-Zn-Mg, ET PRODUITS OBTENUS PAR CE PROCEDE
WO2009156283A1 (fr) * 2008-06-24 2009-12-30 Aleris Aluminum Koblenz Gmbh Produit d'alliage al-zn-mg avec une sensibilité à la trempe réduite
JP2010083381A (ja) * 2008-09-30 2010-04-15 Kobe Steel Ltd バンパーシステム及びその製造方法

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE CAPLUS [online] CHEMICAL ABSTRACTS SERVICE, COLUMBUS, OHIO, US; 8 September 2008 (2008-09-08), XP002658880, Database accession no. 2008:1080285 *
JAYAGANTHAN, R. ET AL: "Effect of cryorolling strain on precipitation kinetics of Al 7075 alloy", vol. 584-586, 2008, MATERIALS SCIENCE FORUM, ISBN: 978-0-87849-375-3, pages: 911 - 916 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108546858A (zh) * 2018-05-29 2018-09-18 广西南南铝加工有限公司 一种7xxx系铝合金板材及其制备工艺
WO2020016506A1 (fr) 2018-07-17 2020-01-23 Constellium Neuf-Brisach Procede de fabrication de toles minces en alliage d'aluminium 7xxx aptes a la mise en forme et a l'assemblage
FR3084087A1 (fr) 2018-07-17 2020-01-24 Constellium Neuf-Brisach Procede de fabrication de toles minces en alliage d'aluminium 7xxx aptes a la mise en forme et a l'assemblage
CN110846598A (zh) * 2019-11-26 2020-02-28 江西江铃集团新能源汽车有限公司 一种铝合金弧焊处理方法
CN113502421A (zh) * 2021-07-13 2021-10-15 山东省科学院新材料研究所 一种Al-Zn-Mg-Fe系铝合金材料及其制备方法与应用
CN113502421B (zh) * 2021-07-13 2022-05-03 山东省科学院新材料研究所 一种Al-Zn-Mg-Fe系铝合金材料及其制备方法与应用
CN113714511A (zh) * 2021-09-23 2021-11-30 中南大学 电弧增材铝合金构件的热处理与深冷变形复合工艺方法

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